1. Technical Field
The present invention relates in particular to a spindle motor to be used in the hard disk drive means, and a hard disk drive apparatus including such a motor.
2. Description of the Prior Art
The motor of the hard disk drive means employs grease or oil as a lubricant to be applied to the bearing.
In such kind of motors, splashing and dispersing of the lubricant from the bearing apparatus into the surrounding environment may be caused by the rotation of the motor. Further, fine dusts suspended in atmosphere is tend to get into the bearing assembly. In order to cope with such problems, some bearings has an annular sealing plate. The sealing structure of the prior art employing such annular sealing plate can be categorized into the contact type and the non-contact type.
In the case of the sealing structure of the non-contact type incorporated into the bearing apparatus, for example, the outer peripheral portion of the annular sealing plate is secured by means of adhesive to the end surface of the outer race with leaving a slight clearance between the inner peripheral portion thereof and the inner race to avoid the contact between them.
However, there is an problem of flowing the lubricant contained within the bearing out through the clearance while the motor is rotated in high speed. In the case of the motor for hard disk drive means, the lubricant flowing out through the clearance will be splashed through the clearance to make oil mist. Thus produced finely dispersed oil mist is apt to get into the disk enclosure of the hard disk drive means. These oil mist adhered on the magnetic disk or the magnetic head will cause the accidents such as the crushing of the magnetic disk and the magnetic head to reduce the reliability of the hard disk drive apparatus.
In order to prevent such accidents as mentioned above, a number of countermeasures have been taken by those skilled in the art. For example, in one of the countermeasures, the annular sealing plate is secured to the outer race around the outer peripheral portion thereof and making the inner peripheral edge thereof contact with the inner race. In such a countermeasure, not only the heat or the torque are produced by the friction between the sealing plate and the inner race, but also the wear due to friction will cause the leakage of the lubricant or produce frictional particles, so that this countermeasure can not be adopted.
Under the reason as mentioned above, the motor including the sealing structure of the non-contacting type as well as an additional labyrinth seal mechanism, or the motor having a magnetic fluid sealing mechanism within the bearing apparatus are available today. However, the additional labyrinth seal mechanism will increase the production cost for manufacturing the motor. When the magnetic fluid is employed to seal, the magnetic fluid is tend to shift radially outwardly under the effect of centrifugal force. Further, the magnetic fluid sometimes splashes under the effect of locally effected differential of air pressure. In conclusion neither of these structure is appropriate to the motor for hard disk drive apparatus. In particular, the additional labyrinth seal mechanism is to be employed, the manufacturer of the motor is required to incorporate such labyrinth seal mechanism into the motor, so that the production cost of the motor is increased.
Accordingly, the object of the present invention is to provide a motor suitable for the hard disk drive apparatus including a labyrinth seal mechanism incorporated into the bearing means to increase the sealing function of the sealing structure of non-contact type to provide a sufficient and reliable sealing function and a hard disk drive apparatus of increased reliability. It is only necessary for the manufacturer of the motor to assemble the motor with the bearing means into which a labyrinth seal mechanism had already been incorporated by the manufacturer of the bearing so that the production cost of the motor can be reduced.